Improved properties of Ti-Al-N coating by multilayer structure

Multinary Ti-Al-N coatings are used for various applications where hard, wear and oxidation resistant materials are needed. Here, we prepare TiAlN/TiN nano-multilayer coatings with modulation period of ~ 20 nm in order to further improve the properties of Ti-Al-N coating. Annealing of both coatings up to 700 °C results in an increase in hardness due to the precipitation of cubic Al-rich domains by spinodal decomposition. Multilayer structure results in an increase in adhesion with substrates from ~ 72 N for Ti-Al-N single layer coating to 98 N for TiAlN/TiN nano-multilayer coating. Additionally, the interfaces of TiAlN/TiN nano-multilayer coating retard the outward diffusion of metal atoms (Al and Ti) and inward diffusion of O while exposing coatings in air atmosphere with elevated temperature, and thus improve its oxidation resistance. An improved machining performance regardless of continuous cutting and milling is obtained by TiAlN/TiN nano-multilayer coated inserts, which can be attributed to the combined effects of higher adhesion with substrates and better oxidation resistance.

Research highlights
► TiN/TiAlN nano-multilayer coating with modulation period of ~20 nm improves the properties of TiAlN coating.
► TiAlN and TiN/TiAlN nano-multilayer coatings behaves age-hardening.
► The better oxidation resistance and adhesion with substrate is obtained by TiN/TiAlN coating.
► TiN/TiAlN nano-multilayer coating obtain improved cutting performance.